Microplastic Contamination in Mangrove Sediments: Environmental Associations and Methodological Heterogeneity

Abstrak

Graphical Abstract Highlight Research 1. Mangrove sediments function as global sinks for microplastics, with accumulation is shaped by the interaction between anthropogenic inputs and natural retention mechanisms, particularly mangrove root density, tidal hydrodynamics, and fine-grained sediments. 2. Fibers and fragments dominated the recovered particles, with polyethylene (PE) and polypropylene (PP) consistently identified as the predominant polymers. 3. Urbanization, wastewater discharge, riverine transport, tourism, fishing, and aquaculture are major pathways contributing to microplastic accumulation in mangrove sediments. 4. Methodological heterogeneity, particularly density separation media, particle-size thresholds, and visual identification, substantially limits cross-study comparability. 5. International standardization of sampling, high-density flotation, contamination controls, and spectroscopic polymer confirmation is essential for reliable global monitoring of mangrove microplastics. Abstract Mangrove sediments retain microplastics, yet their contamination patterns remain difficult to compare across environmental settings and analytical methods. This systematic review synthesized reported microplastic abundance, particle composition, environmental associations, and methodological heterogeneity in mangrove sediments. A Scopus search identified 97 records, of which 37 empirical studies were retained following title and abstract screening, full-text retrieval, and eligibility and quality assessment. Evidence was synthesized narratively and thematically, with abundance values preserved in their reported units rather than pooled across incompatible methods. Reported abundances ranged from approximately 12 to more than 6,000 particles kg⁻¹ dry sediment among studies using that unit, with research concentrated in Asian mangroves and additional evidence from Brazil. Fibers and fragments were frequently predominant, while polyethylene and polypropylene were commonly identified polymers. Reported distributions varied substantially with mangrove vegetation and root structure, hydrodynamics, sediment characteristics, and anthropogenic pressures, including urbanization, wastewater discharge, fisheries, aquaculture, tourism, and maritime activities. These associations do not independently establish the relative causal contributions of individual sources or environmental processes. Sampling depth and design, particle-size thresholds, density-separation media, contamination controls, and spectroscopic polymer verification differed across studies, limiting direct comparison of reported concentrations. The review therefore describes recurring observations rather than estimating globally representative microplastic abundance. Its evidence base was further constrained by reliance on Scopus, inaccessible full texts, and uneven geographical coverage. More consistent reporting of sampling and analytical procedures, appropriate contamination controls, reliable polymer confirmation, and geographically broader investigations are needed to strengthen comparisons and clarify contamination patterns across mangrove sediment environments.

Kata kunci

• Mangrove sediments
• Microplastic abundance
• Environmental drivers
• Polymer composition
• Methodological heterogeneity